Pivot retainer



Nov. 21, 1950 N. E. HART 2,531,125

IN V EN TOR.

Norma/7 5. H07 Y J5 w z wm Patented Nov. 21, 1950 PIVOT RETAINER Norman E. Hart, Toledo, Ohio, assignor to Toledo Scale Company, Toledo, Ohio, a corporation of New Jersey Application 1...... 2, 1945, Serial No. 597,361

2 Claims.

This invention relates to Weighing scales and in particular to an improved method for mounting knife edges in a heavy capacity lever.

Because of the high cost of steel suitable for use as knife edges in a scale the knife edges of heavy capacity scale levers are usually constructed of a relatively small bar of high-quality steel supported throughout its length on a heavier bar of ordinary steel. The second bar, the heavy bar, extends through a hole bored transversely through a scale lever. This type of construction, while economical, presents sev eral difliculties. Among these difficulties is the problem of suitably securing the heavy bar in the hole in the lever so that it can not twist or rock from side to side, the problem of securing the knife edge bars in the heavy pivot retaining bar and finally of providing suitable thrust bearings without weakening the scale lever.

The object of this invention is to provide a novel assembly of elements in which a key used to lock a pivot retaining bar in a scale lever also serves as thrust hearings on either side of the lever. I

Another object of the invention is to provide an improved pivot support for a heavy capacity scale lever which support may be mounted in a cylindrical hole in the scale lever.

Another object of the invention is to provide a novel pivot support for a scale lever which may be very securely mounted in a scale lever but which may be very easily removed if replacement is necessary.

These and other objects and advantages areapparent from the following description in,which reference is made to the accompanying drawings illustrating preferred embodiments of the invention.

In the drawings:

Figure I is a fragmentary perspective view of one end of a heavy capacity lever showing an improved pivot support installed therein.

Figure II is a fragmentary end elevation, partly in section, showing the details of the improved pivot support.

Figure III is a fragmentary side elevation, partly in section, as seen from the line IIIIII of Figure II.

Figure IV is an end elevation, partly in section, showing another embodiment of the invention.

These specific drawings and the accompanying description are intended merely to illustrate the invention and not to impose limitations on the claims.

According to the present invention the problem of suitably mounting a knife edge support in aheavy capacity scale lever and providing thrust bearings is solved by employing a key whose hardened ends protrude slightly on either side of the scale lever adjacent the inner ends of knife edge pivots supported in a bar extending transversely through the lever. The under surface of the key is tapered so that after the key and the pivot retaining bar are inserted in the lever a Wedge or wedges may be driven into the keyway in the bar beneath the key and thus securely anchor the key and the bar into the lever.

This improved construction avoids any extra machining operations on the lever as Well as the weakening of the lever which inevitably occurs when ordinary pivot thrust bearings are installed. The improved structure also eliminates the thrust bearing which in prior constructions extended above the pivot line in position to interfere with the V-bearing resting on the knife edge.

Illustrative examples of the invention are shown in the drawings. In the first example an end portion l of a heavy capacity weighing scale lever 2 has a transverse bored hole 3 provided with a keyway 4 in its upper periphery. The hole 3 and the keyway 4 are positioned such that the keyway 4 is approximately on the pivot line of the lever. A cylindrical pivot retaining bar 5 whose diameter is such that it is a close fit in the bored hole 3 is provided with a keyway 6 whose width and depth is sufiicient to accommodate knife edge bars I and hold them in proper alignment when the lever is in use.

A hardened double ended gib key. 8 having tips 9 extending upwardly on each side of the lever end I is positioned in the keyways 4 and 6 so as to prevent any rotative movement of the pivot supporting bar 5. The gib key 8 tapers from the ends toward the center so that a pair of wedges l0 and l I may be driven into the space between the bottom of the keyway 6 and the key 8 so as to lock the pivot retaining bar 5 and the key securely in the lever. By providing two, wedges whose taper corresponds to the slope of the bottom of the gib key 8 and driving these wedges in from opposite sides of the lever all tendencies for the pivot bar 5 to rock or loosen in service are eliminated.

In a second example of the invention a pivot supporting and retaining bar I2 is inserted in a transverse bore through a lever I3. The pivot support bar l2 and the lever I3 are provided with aligned keyways l4 and I5. A tapered key l6 fully seated in the keyway 15 in the lever and partially engaged in the keyway [4 of the retaining bar I2 is provided to prevent any rotation of the pivot retaining bar I2 in the hole of the lever I3. The tapered key 16 is held in place by a wedge 11 driven into the keyway l4 below the tapered key Hi. The key l6 and the wedge I! have the same degree of taper so .that when they are wedged together their outer surfaces are parallel and uniform pressure is exerted between the pivot retaining bar 12 and the lever l3 throughout the length of the key [6 and wedge 11. The length of the key 16 is slightly greater than the thickness of the lever 13 so that it protrudes slightly beyond each side of the lever.

A pair of knife edge bars 18 and 19 are fitted into the keyway M of the pivot retaining bar 12 and are of such height that their knife edges 29 and 2! lie slightly below the plane of the upper surface of the key IS. The ends of the key 16 are smoothed and hardened so that they may serve as thrust bearings adapted to position the -bearings supported on the knife edges 29 and 2|.

While the single wedge offers a somewhat simpler construction it requires greater precision in manufacture to insure uniform distribution of pressure throughout the length of the key and wedge. However this disadvantage is ofiset by the fact that the key it and wedge I! may be removed in the event it becomes necessary to replace the pivot supporting bar 12. The double wedge arrangement shown in the first example, while it aiiords a somewhat more uniform distribution of pressure, can not be disassembled once the wedges have been firmly set.

The utilization of the keys as thrust bearings in addition to their use as keys to prevent rotation of the pivot retaining bar reduces the number of machining operations necessary in the manufacture of the lever and avoids the weakening of the lever which occurs when separate thrust bearings are employed. Besides these advantages the use of a key as thrust bearing eliminates most of the thrust bearing structure extending above the pivot line and thereby reduces the possibility of interference between the V-bearing of the thrust hearing or adjacent parts of the lever.

Having described the invention, I claim:

1. A weighing scale lever and pivot construction comprising a lever having a transverse bore provided with a keyway, a pivot support bar that fits through the bore, said bar having a longitudinal keyway, a first wedge shaped key inserted in the keyways of the lever and the bar with its ends extending beyond each side of the lever and radially outside the periphery of the bar, said key having end surfaces perpendicular to its length, at least one other wedge shaped key located in the keyway of the bar for locking the first key in position, and a pair of knife edge pivots mounted in the keyway of the support bar with an end of the knife edge of each pivot juxtaposed to an end surface of said first key.

2. A weighing scale lever and pivot construction comprising a lever having a transverse bore provided with a keyway, a pivot support bar that fits through the bore, said bar having a longitudinal keyway, a U-shaped key having a wedge shaped center section inserted in the keyways of the lever and bar with its end sections extending radially beyond the keyways at each side of the lever, said end sections each having a surface parallel to the lever, at least one wedge located in the keyway of the bar for locking the key in place, and a pair of knife edge pivots mounted in the keyway of the bar with one end of each pivot juxtaposed to an end surface of the key.

NORMAN E. HART.

REFERENCES CITED The following references are of record in the file of this patent:

UNIT-ED STATES PATENTS 

